Firefox 0 Day

This security vulnerability is being actively exploited. Stop using Firefox under Windows until patched.
“Currently it exploits Windows systems with a high success rate and affects Firefox versions 41 to 50 and the current version of the Tor Browser Bundle”
More info:
Emergency Bulletin: Firefox 0 day in the wild. What to do. – Wordfence blog
Firefox 0day in the wild is being used to attack Tor users – Arstechnica